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PH Meter tips and Qs

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majorvices:
Dug my pH meter out and was surprised to see that after several months it seems to work just fine even though I was out of storage solution and stored it dry since the summer. Anyway - I ordered more solution and have some questions:

#1 - can you reuse the calibration solutions? Seems stupid to just pour them out afterward. But I do because i don't know how stable they are,

#2 - Do you need to rinse the calibration solution between tests? I do (with tap water) but was wondering if this skewed the results.

#3 - how exactly do you store the meter? I am currently storing it on the kitchen counter in a Kolsch Stang filled with storage solution to cover the tip. That is a pain though. How much longer will the solution preserve the tip compared to stroing it dry in the case? Seemed to work fine for several months for me. What's the deal?

Kaiser:

--- Quote from: majorvices on December 29, 2009, 10:22:09 AM --- #1 - can you reuse the calibration solutions? Seems stupid to just pour them out afterward. But I do because i don't know how stable they are,

--- End quote ---

You are not supposed to but you can. I do that b/c I’m cheap. I have 500 ml of the 7.00 and the 4.00 buffer and keep about 2 oz of each in the small 4 oz bottles that came with the buffer I purchased from the HBS a while back. About every 6 month I replenish the buffers and the meter shows a difference of about 0.01 – 0.02 between the old and the new.

Buffer solutions are very stable. They are strong buffers and if you rinse your probe with RO or distilled water before you put it into the buffer, you are not adding any acids or bases that could chance the acid/base balance in the buffer.


--- Quote ---#2 - Do you need to rinse the calibration solution between tests? I do (with tap water) but was wondering if this skewed the results.

--- End quote ---

Yes, you have to rinse the probe. And you need to use very soft or distilled water. If you don’t rinse, you’ll get too much mixing of the two buffers over time that it will start to make a difference. Both buffers are strong enough that that they can affect each other. DI water has no strength and there is no problem if you get a drop or two of that into the buffers.


--- Quote ---#3 - how exactly do you store the meter? I am currently storing it on the kitchen counter in a Kolsch Stang filled with storage solution to cover the tip. That is a pain though. How much longer will the solution preserve the tip compared to stroing it dry in the case? Seemed to work fine for several months for me. What's the deal?

--- End quote ---

I build a little holder for my pH meter:



The probe sits in an empty pill bottle filled with storage solution. I drilled a hole in the cap that fits the probe exactly. You want to minimize evaporation.

Kai

Kaiser:
One more thing. You didn’t ask but I want to share this.

If you take good care of your pH meter (stored in storage solution, no testing of hot liquids and proper rinsing of the probe after each use) then you can get away with calibrating it every few weeks. I used to run a lot of pH experiments and calibrated it before running these experiments and there was hardly any drift in the calibration. Maybe 0.01 – 0.02. But that is so small with respect to the pH ranges that we care about that it doesn’t matter much.

I now only calibrate it about every 2 weeks. And between these times I just use it w/o the effort of calibrating it. Let’s face it, if you have to spend a minute or more calibrating it every time you need to test the pH of something it would become a hassle pretty soon and you would stop testing pH. And how big is the error going to be? 0.02 at most, in my case. And it is not that you wouldn’t notice that something is wrong by getting an unexpected measurement or next time you calibrate the meter.

Kai

lonnie mac:
Say Kai, what meter is that? I have seen it before. I like the remote probe it has...

I have the Jenco 618. Been using it and abusing it for about 5 years now! I can't believe the silly thing is still going strong on my original probe through well over a hundred batches now. I can say a few things though... I have always used RO water for cleaning and rinsing during calibrations. But I have always used this thing in the mash too. So I would say that it has been regularly subjected to 150 +/- f. It is an ATC model... I have always wondered too about throwing out my calibrations solutions, or even if they are getting old and loosing their oomPh so to speak... I would hate to have known that I am calibrating using solutions that are not correct! Id say the solutions are 5 years old just like my meter. The little Jenco 618 has a nice storage cup that fits over the probe so I have never ran it dry, but honestly, I am thinking that these little things are pretty resilient, and can last a very long time with reasonable care.

What say ye watermaster?

Kaiser:
It’s the Milwaukee SM101. It has served me very well and I like it much better than my old pH 53 which had ATC and micro processor controlled calibration.

I advice against testing hot mashes because of the added stress to the probe and the ambiguity about the pH shift that actually happens between room temp and mash temp. Everybody cites the magical 0.35 correction but when I tested that it was only like 0.2. Mash pH guidelines in the technical literature are almost always given for cooled wort samples and by testing cooled wort I don’t have to worry how much pH shift there actually is.

But it seems that your probe has defeated the odds and is still going strong. I might be a bit overly protective of mine but it can’t hurt. But having a meter with BNC connector for the probe I can also replace it with a 3rd party one and don’t have to rely on Milwaukee for a replacement.

Kai

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